1. Field
Aspects of the present invention relate to high speed rod rolling mills, and more particularly to improvements to the laying heads employed in such mills to form the hot rolled product into a helical series of rings.
2. Description of Related Art
With reference to FIG. 1, a conventional laying head 10 includes a housing containing a rotatably driven hollow quill 12. The quill is subdivided into a tubular body 12a journalled for rotation between axially spaced bearings 14, 16, and a nose 18 detachably secured by means of a mounting flange 20 to the tubular body 12a. The nose projects axially and forwardly in cantilever fashion from the tubular body.
The quill 12 carries a product guide, typically in the form of a three dimensionally curved laying pipe 22. The laying pipe has an entry end 22a aligned with the rotational axis “X” of the quill 12, and a curved intermediate section 12b leading to a delivery end 22c spaced radially from axis X.
Hot rolled steel rod is directed into the entry end 22a of the laying pipe 22 along axis X, and exits from the delivery end 22c as a helical formation of rings (not shown). Upon exiting from the delivery end 22c of the laying pipe 22, the rings are additionally confined and moved forward by a helical guide trough 24 surrounded by a cylindrical shroud 26. The guide trough 24 is configured and dimensioned to coact with the shroud 26 in providing an axially and radially confined helical extension of the guide path defined by the laying pipe 22.
Although this extended confinement has proven to be highly beneficial in resisting distortion and kinking of the tail ends of products as they exit from the laying head 10, the manner of supporting the guide trough 24, as well as its design, have given rise to difficulties that have been found to compromise high speed operation of the laying head.
For example, the curved intermediate portion 12b of the laying pipe 22 is supported on the nose 18 by radially projecting struts 28, whereas the guide trough 24 is carried on a separate disc-shaped trough support 30 detachably mounted on the end of the cantilevered nose 18.
With further reference to FIGS. 2 and 3, the disc-shaped trough support 30 may be seen as including a hub 32 at the center of a helical plate 34 on the outer rim of which are attached channel-shaped trough segments typically indicated at 24′.
The helical plate 34 is typically welded to the hub 32, with the resulting structure of the trough support 30 being robust and consequently heavy in order to withstand the stresses resulting from high speed operation of the laying head. Moreover, difficulties are encountered in accurately aligning the trough support 30 with the rotational axis X of the laying head, with even slight misalignments causing disruptive vibrations at high speeds.
An additional drawback relates to the conventional trough segments 24′, which typically comprise unitary expensive investment castings. The traditional casting materials have been found to lack adequate resistance to wear occasioned by frictional contact with the hot rolled product. Attempts at dealing with this problem have included increasing the thicknesses of the trough segment side walls, but the resulting increased weight has been found to further contribute to instability of the laying head.